RFR: 8371956: Convert OopStorage to use Atomic<T>

[Kim Barrett]

Please review this change to OopStorage to use Atomic<T> rather than directly
applying AtomicAccess to volatile members.

Testing: mach5 tier1-5

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Commit messages:
 - OopStorage uses Atomic<T>

Changes: https://git.openjdk.org/jdk/pull/28338/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28338&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8371956
  Stats: 103 lines in 5 files changed: 8 ins; 2 del; 93 mod
  Patch: https://git.openjdk.org/jdk/pull/28338.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28338/head:pull/28338

PR: https://git.openjdk.org/jdk/pull/28338